Design & Test

Final Report of FCC Working Group: Lose LightSquared from L-Band

July 6, 2011By

“Based on the analysis performed, LightSquared should not be permitted to use the L-Band spectrum for a densely-deployed, non-integrated terrestrial-only network. Such a network would cause unacceptable interference to GPS operations, wiping out an installed base of over 500 million units used in a wide array of public safety, aviation, industrial and consumer applications. While mitigation techniques utilizing filters were discussed in theory, they could not be tested as part of the WG effort because filters do not exist, even in prototypes. No information considered by the WG demonstrated that any mitigation techniques — other than relocation of the proposed terrestrial network to an alternative band — would be successful.” (From the U.S. GPS Industry Council's overview of the WG report) read more

This article is tagged with , and posted in Design & Test, GNSS

Innovation: Multipath Minimization Method

July 1, 2011By
Fig2-W(top)

Mitigation Through Adaptive Filtering for Machine Automation Applications
Multipath is real and omnipresent, a detriment when GPS is used for positioning, navigation, and timing. The authors look at a technique to reduce multipath by using a pair of antennas on a moving vehicle together with a sophisticated mathematical model. This reduces the level of multipath on carrier-phase observations and thereby improves the accuracy of the vehicle’s position. read more

This article is tagged with , , and posted in Design & Test, From the Magazine, Innovation

The System: LightSquared Interference with GPS

July 1, 2011By

And the Beat Goes on Developments in the LightSquared saga came fast and furious in June; highlights are listed below and briefly recapped in the adjacent news story. It will be dated by the time you receive this issue, as it went to press three weeks prior. For current events, see Top Story and Latest News, and the full versions... read more

This article is tagged with and posted in Design & Test, GNSS, Survey, The System, Transportation

Lone Sentinel: Single-Receiver Sensitivity to RF Interference

July 1, 2011By
Tong_open2

Using signal-to-noise measurements from a single commercial-grade L1 GPS receiver, it is possible to detect interference or jamming that is above the thermal noise floor and below a power that causes loss of position. read more

This article is tagged with , , and posted in Design & Test

How GPS and GLONASS Got Together — and Other Recent Events

June 1, 2011By
Javad_Opener

The recent broadcast of the first CDMA signal from the new GLONASS-K satellite culminates a long series of events that began in 1989. A key participant gives a first-hand account of the history of many meetings, formal and informal, that created true interoperability between the two major satellite systems, giving users a modern GNSS in action. read more

This article is tagged with , , , and posted in Design & Test, GNSS

Innovation: Doppler-Aided Positioning

May 1, 2011By
Figure 1. Satellite tracking and carrier-phase anomaly summary during the observation time-span. These data were collected in a dense urban environment in both static and kinematic mode. The superimposed red-points show epochs where carrier-phase observables are either missing or contaminated with cycle slips, loss of locks, and/or other measurement anomalies.

Improving Single-Frequency RTK in the Urban Enviornment
A look at how Doppler measurements can be used to smooth noisy code-based pseudoranges to improve the precision of autonomous positioning as well as to improve the availability of single-frequency real-time kinematic positioning, especially in urban environments. read more

The System: Second Report by LightSquared/GPS Technical Working Group Maps Terrain, Does Not Yet Explore

May 1, 2011By

Plus: GLONASS CDMA Tracked, Third Beidou-2 Launched The second report from non‐governmental members of the LightSquared/GPS Technical Working Group (TWG) was filed with the Federal Communications Commission (FCC) on April 15. For those anxious to see actual results of interference/desensitization of GPS receivers by the proposed LightSquared terrestrial signal — or, conversely, absence of said results — the report does not contain... read more

This article is tagged with , and posted in Design & Test, The System

Future Wave: L1C Signal Performance and Receiver Design

April 1, 2011By
L1C-3

The new GPS L1C signal will be broadcast by the Block III satellites, with first launches as early as 2014. L1C innovations significantly enhance PNT performance as well as interoperability with other GNSS signals. The authors describe the benefits of its new features and how best to make use of each one. read more

This article is tagged with , , , , and posted in Design & Test